The invention is directed to a process for the separation of glycomacropeptide or caseinoglycomacropeptide (xe2x80x9cGMPxe2x80x9d) from lactic raw material.
GMP is a phosphorylated and partially sialylated macropeptide which is formed by the action of a protease, for example rennet, on mammalian milk kappa-casein. GMP represents about 20% by weight of the proteins in sweet whey obtained after separation of casein during cheese manufacture.
A laboratory scale process for the manufacture of GMP is known. The process consists of treating a raw lactic material, such as an acid casein, a caseinate hydrolyzed by rennet, or a demineralized and lactose-free sweet whey from cheesemaking, with trichloroacetic acid so as to precipitate the proteins. The process further consists of recovering the supernatant, dialyzing the supernatant, and drying the separated dialysate. Although known, such a process is not applicable on an industrial scale.
A process for the production of GMP on an industrial scale, which is described in European Patent Application No. 488,589, consists of treating a whey product by ion exchange and recovering the fraction that has not been adsorbed. The process further consists of concentrating the fraction, demineralizing the fraction using ultrafiltration, diafiltration and, if necessary reverse osmosis, and recovering the GMP.
British Patent No. 2,188,526 discloses a process for the production of a whey protein fraction. The process consists of treating a milk product with a strong anionic resin, under conditions such that proteins and some peptides of the treated material are nonselectively adsorbed onto the resin in the form of complexes. These complexes are difficult to subsequently elute from the resin. The eluate forms a firm gel at a pH of less than 4.5 and at room temperature, once the eluate is suspended in water. The protein fraction may be used in drinks of the milk-shake type and in dessert mousses.
Japanese Patent Publication Kokai 07-132049 uses a weakly anionic ion exchange resin whose matrix is hydrophilic to separate the sialylated peptides from whey. The process consists of passing the raw material, whose pH has been beforehand precisely adjusted to a value of 4 to 6, over a hydrophilic macromolecular support consisting of a natural polysaccharide or a synthetic polyvinyl, grafted with basic exchanging groups. The supports used as matrix are not easily applicable industrially.
Despite the aforementioned processes, there is a need for a process which easily and selectively separates a highly purified GMP from lactic raw materials without additional expense and which can be conducted on a large scale. Additionally, it is highly desirable to develop a process that can separate GMP from lactic raw material in a single operation and in high yield.
The invention relates to a process for the extraction of GMP from a lactic raw material comprising the steps of removing cations from a lactic raw material for a sufficient amount of time to obtain a substantially deionized lactic raw material having a pH of about 1 to 4.5; contacting the substantially deionized lactic raw material with an anionic resin having a hydrophobic matrix for a sufficient amount of time and at a sufficient temperature to remove GMP from the substantially deionized lactic raw material and to obtain a treated liquid material; separating the resin from the treated liquid material; and rinsing the resin to obtain the GMP therefrom.
In this process, the lactic raw material can be one of sweet whey obtained after separation of casein coagulated with rennet, a concentrate of sweet whey, a sweet whey or such a whey demineralized to by electrodialysis, ion exchange, reverse osmosis, electrodeionization or a combination of these procedures, a concentrate of sweet whey demineralized by electrodialysis, ion exchange, reverse osmosis, electrodeionization or a combination of these procedures, a concentrate of proteins of substantially lactose-free sweet whey obtained by ultrafiltration, followed by diafiltration (ultrafiltration with washing), mother liquors of the crystallization of lactose from sweet whey, a permeate of ultrafiltration of a sweet whey, the product of hydrolysis, by a protease, of a native casein obtained by acid precipitation of skimmed milk with an inorganic acid or by biological acidification, where appropriate with addition of calcium ions or alternatively of a micellar casein, obtained by microfiltration of a skimmed milk, the product of hydrolysis of a caseinate by a protease. Preferably, the sweet whey has a solids content of about 10 to 23 percent by weight and is completely deionized during the cation removal step.
Also, the lactic raw material is preferably a liquid or a dispersion of solids in a liquid and calcium ions may be added to the lactic raw material after the cation removal step.
Advantageously, the resin is treated with an alkaline material prior to contact with the substantially deionized lactic raw material. Preferably, the substantially deionized lactic raw material contacts the resin in a gently stirred reactor at a temperature of less than 50xc2x0 C. for one to ten hours to adsorb the GMP onto the resin. A suitable resin is one that is basic and in macroporous or macrocross-linked gel form. The substantially deionized lactic raw material usually contacts the resin until the treated liquid material attains a constant pH of between about 4.5 to 5.5 to indicate that the reaction has proceeded to completion. Advantageously, the resin and lactic raw material are present in a volume ratio of 1:1 to 1:30.
The invention also relates to the treated liquid material that is obtained from this inventive process. This treated liquid material has an amino acid profile is reduced in threonine and enriched in aromatic amino acids and tryptophan. Relative to the starting lactic raw material, the threonine content is preferably reduced by about 15 to 40%, and the aromatic amino acids and tryptophan are preferably increased by about 20 to 60%. This treated liquid material is useful in an infant or dietetic product as a protein raw material, in a pharmaceutical composition in combination with antithrombotic, antidiarrheal or antibacterial agents, or in a food composition as an emulsifying, gelling or foaming agent. The invention also produces a new GMP which can be used, for example, in a dental composition as an agent against plaque and caries.